MNSBR: Super Grom Build - MNSBR

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Super Grom Build

#46 User is offline   POE Icon

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Posted 13 June 2018 - 03:32 PM

 nOOb, on 13 June 2018 - 03:26 PM, said:

Yea the unfortunate thing is that a fuel controller and its other components costs just as much as the kit itself. Are you sure the stock O2 sensor is sufficient?

I'm tempted to just run a BBK if I'm spending $500+ on a fuel controller and wideband sensor.


Stock O2 sensor is a narrow band sensor and it's installed in the head in the exhaust port. Stock ECU uses it just fine.

If I would have known I was getting in this deep with the kit I would have researched BBKs more first. But the reliability is a problem with BBKs.
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Posted 13 June 2018 - 03:42 PM

I'm still thinking I must have setup something wrong. It just doesn't make sense to change this much on a motor and have such a minimal gain. I understand it's only 125cc, but still.
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Posted 14 June 2018 - 09:54 AM

The last few rides I've thought that, yes, it does have more power, but just not as much as I would have expected. I imagined nearly doubling the horse power (supposedly) would carry more than 60mph sitting up. I could already get 55mph sitting up on a stock motor.
I also need to consider the fact that I have not ridden a stock Grom in a few weeks. I should take out my stock Grom for a rip and compare the feeling to the built Grom. I still think that won't explain the dogginess of the new build. It's either something put together wrong, or trying to make the stock (but highly modified) air box work is effecting things more than I can imagine.

Here's the plug:

Posted Image


Posted Image

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Posted 15 June 2018 - 08:13 AM

Revealing update:

I rode a buddy's Super 125 Grom that was put together with a Power Commander 5, wide-band O2 sensor, custom map and ignition module. Basically all the high end crap I really didn't want to pay for.

Result: I rode his Grom, got onto the first open straight and cracked it open. It didn't blow my mind, but had some very serious low to upper-mid range grunt that mine is lacking. The top end (9k-12.5k redline) was very similar. He had stock gears where as mine are currently -1/+1, but I figured that into what I was observing. Sitting up on his Grom, I was not able to get to a true 60mph, probably 58. It was windy, but still couldn't get up to 60 after we turned around. His Grom definitely has the hole shot and middle power I'm craving.

One more note before my conclusion... I took the front airbox cover off this morning and just screwed the Koso high-flow filter directly to the box so there would be no air flow impedance from the cover. It made no difference. This air filter should have very minimal flow restriction.

Conclusion:
I need a fancy expensive fuel controller to get my idle-9k power that I expected. I didn't want to be 'that guy', but if I'm in it this far, I might as well do it right. I won't buy it right away, but I'll eventually get around to it. I wouldn't doubt it if I put it off to winter or next spring. I'm still at about the same low end power as the stock engine, but mid range is a tick more. I'll get this thing geared properly for the power I do have now and it will definitely be a solid improvement overall.

Recommendation:
If you have the desire to build a little bike, the Super 125 will get you some good results if you pay for the fancy computer and maintain some very solid reliability. This just comes at a higher cost than a BBK.
If you went BBK, you would sacrifice reliability, but get cheaper power gain and likely have more low-mid torque, which is what I miss. I like wheelies, so the torque would be nice. But at least I know I'll have the low-mid power back once I get a real fuel programmer.

If I know you, feel free to ask for a test ride if you're curious about this build.

Anyone know much about the ARacer RC Mini 5 vs Power Commander?


No front airbox cover

Posted Image




Changed up the color. Hindle exhaust looks good. I heard someone else ride it yesterday and it's not as loud as I imagined it to be (w/ baffle), but it's still loud.

Posted Image
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#50 User is offline   Vrooom Icon

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Posted 15 June 2018 - 08:30 AM

Can your friend hit 60mph? Im curious of rider weight? Im getting that Rs2 yoshi system. Think he is throwing in ear plugs too haha. I will have to toss the gps on it after to figure out my top speed again.
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#51 User is offline   crakerjac Icon

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Posted 15 June 2018 - 08:32 AM

Do you think your stock Grom would have anything from 9-12k (in 3rd)? Assuming that the rev limiter was raised? I'm trying to sort out something on my Z, but don't know anyone else with a Z to compare it to... so Grom is probably 'close enough'.
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Posted 15 June 2018 - 08:47 AM

View PostVrooom, on 15 June 2018 - 08:30 AM, said:

Can your friend hit 60mph? Im curious of rider weight? Im getting that Rs2 yoshi system. Think he is throwing in ear plugs too haha. I will have to toss the gps on it after to figure out my top speed again.

He's 250lbs. He said he can get over 60. I'm sure that's with ideal or beneficial conditions. His 4th gear was stalling out at about 7500 - 8000 rpm and not accelerating. If he gears down, his bike will be a beast.

View Postcrakerjac, on 15 June 2018 - 08:32 AM, said:

Do you think your stock Grom would have anything from 9-12k (in 3rd)? Assuming that the rev limiter was raised? I'm trying to sort out something on my Z, but don't know anyone else with a Z to compare it to... so Grom is probably 'close enough'.


Stock redline is 9500 rpm. So no, not pull much there. If the limiter was raised on the stock bike, the power starts to drop off after 9k, so it wouldn't matter much. I believe that to be an issue with air flow on the tiny diameter intake/exhaust. But, 3rd gear on stock Grom still accelerates through the entire range in neutral road/wind conditions.

One more thing I'm considering is going back to a stock 420 chain and sprocket setup and sell the 428 as slightly used. A couple big shot grom mechanics said the extra weight of a 428 isn't necessary. If you buy a high quality 420 chain it won't stretch with the type of power this kit makes. The lighter rotating mass will help free up some power. And I got to thinking, if dropping from a 530 or 525 down to a 520 is useful on a big bike, dropping from 428 to 420 should be a measurable difference.
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Posted 20 June 2018 - 08:20 AM

View PostPOE, on 15 June 2018 - 08:13 AM, said:

Anyone know much about the ARacer RC Mini 5 vs Power Commander?


When I do decide to get a tuner, I'll go with an ARacer unit. Either the "2" or the "5" model. The 5 interfaces through a cell phone and bluetooth, but as nice as that sounds, you have to pay $16 for the fully unlocked app (one time, or annual, I don't know), The "2" model can plug into a laptop, which seems more reliable to me. They're both about the same price, so I gotta research a bit more about any real differences between the two.

I found out that if I put in a whole quart of oil (instead of 0.9qt) I get a whole hell of a lot of oil blowing out through the crank case breather. My airbox was leaking quite a bit of oil onto the ground. I really hope this is just from overfilling the oil. If it's something else, my guess would be piston blow-by from bad ring seals causing excessive case pressure. But I know I installed the piston properly, honed the cylinder, clocked the rings, used assembly lube to install and did a pretty easy break-in procedure.



Next up:

-Go back to 420 chain/sprockets and 14/37 gears (what I had on my stock build), since I already have these laying around. I think I'll end up more aggressive than this -1/+3 ratio if I still can't get into the power in 4th gear.

-During the next oil change (as soon as I have time) I will install my high-flow oil pump with a pickup line that runs to the back of the case. If I have time, I'll install my oil cooler, too. I may need an aftermarket intake just so I can eliminate the stock airbox to make room to mount the cooler.
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#54 User is offline   sk8phreak88 Icon

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Posted Yesterday, 12:00 AM

Man, Sorry the results aren't what you were expecting. I was really hoping you'd be on here posting something like "This thing is STUPID FUN!"

Things like this just make me think I should keep it stock and just deal with it being slow.
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Posted Yesterday, 01:08 AM

I appreciate the honest review. Too many guys are ashamed to do so after spending the coin on a project. So they rave about how badass it is.
Hope you find the magic formula Luke.
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#56 User is offline   Kent Larson Icon

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Posted Yesterday, 07:37 AM

View Postsk8phreak88, on 22 June 2018 - 12:00 AM, said:

Things like this just make me think I should keep it stock and just deal with it being slow.


I'm happy enough with the Grom in stock form. I road in on 94 again this morning because I have Twins tickets and the Grom can park with the scooters in the bike racks.
Had no problem keeping up with traffic for the 20 miles I stayed on 94 from Woodbury to Minneapolis. Most of the time I was sitting tall doing about 60 with the cables stretched tight on level ground with a slight draft. Sometimes I needed a full tuck to pass or catch up to the car ahead while indicating 68-70mph.

Full tuck and drafting showed 72mph a few times at about 9800rpm. That's well into the red line but not hitting the limiter. (Does this even have a limiter? I should look that up.)

Anyway, fun enough stock but I know I'm giving her way too much abuse. We'll see how much it can take before she blows up.

Later,
Kent Larson from Woodbury
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Posted Yesterday, 08:29 AM

I think you just need to break down and do a 300 swap on it and be done. Looks like you can buy a kit to take care of most of the fabrication work. All you need to do is source a CB250/300 motor splice a few wires and call it a day.

Nothing like that for the Z, so I will be flogging my bike in stock form for the foreseeable future... although fastest I've ever seen is 64 (downhill) on my Z, so I'm quite jealous of Kent's indicated speeds.
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Posted Yesterday, 08:36 AM

View Postcrakerjac, on 22 June 2018 - 08:29 AM, said:

I think you just need to break down and do a 300 swap on it and be done. Looks like you can buy a kit to take care of most of the fabrication work. All you need to do is source a CB250/300 motor splice a few wires and call it a day.

Nothing like that for the Z, so I will be flogging my bike in stock form for the foreseeable future... although fastest I've ever seen is 64 (downhill) on my Z, so I'm quite jealous of Kent's indicated speeds.


Got a deal I couldnt pass up on a full yosh exhauts for the Z. Will see if it helps top end at all. I havent had the chance to flog it yet. Its loud! Even with the baffle in.
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#59 User is offline   crakerjac Icon

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Posted Yesterday, 08:39 AM

View PostVrooom, on 22 June 2018 - 08:36 AM, said:

Got a deal I couldnt pass up on a full yosh exhauts for the Z. Will see if it helps top end at all.


Keep me posted. I've got a Zoom loop and my top end is crap.
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